This invention relates to a writing and metering device.
Such a device is known from Great Britain patent No. GB 2 118 486 A. As disclosed in that patent, a semi-permeable seal and an adjoining non-capillary space at the front end of the ventilation channel are intended to serve as an anti-escape mechanism to prevent the escape of ink. Although the membrane-like seal prevents the escape of ink via the ventilation channel, at this point it cannot prevent ink dripping via the writing tip following one or more large changes in pressure and/or temperature. This is because ink which escapes into the non-capillary space cannot be drawn back into the ink supply chamber. This results in an enclosed volume of air which can lead to leakage when there are large variations in pressure and/or temperature.
A device mentioned at the outset is intended to be improved by the present invention in such a way that ink which has escaped under the influence of pressure and/or temperature is always drawn back into the ink supply chamber and a constant ventilation of the ink supply chamber is guaranteed.
This object is achieved according to the present invention by a writing and metering device with an ink supply chamber, an ink holder, with a capillary ink regulator, leading from the ink supply chamber to the writing wick, and with a ventilation channel connected to the ink supply chamber, a first non-capillary space and a semi-permeable seal which is impermeable to ink, characterized in that the first non-capillary space and the semi-permeable seal are connected, via a second non-capillary space and the latter via at least one capillary, to the ink supply chamber.
The arrangement of the semi-permeable seal within the writing device as well as of two non-capillary spaces in front of and behind the semi-permeable seal together with at least one capillary channel, or connection, between the hindmost non-capillary space and the ink supply chamber results in unusually good security against leakage of ink. The capillary connection ensures that ink which has escaped behind the semi-permeable seal is drawn back into the ink supply chamber and that a constant ventilation of the ink supply chamber is guaranteed.
A labyrinth vent in the ventilation channel in front of the first non-capillary space and the semi-permeable seal serves additionally to reduce ink losses when the writing device is stored with the cap removed.